I have some GT40P heads on my 89 GT, how do these compare? I see these have larger combustion chambers so I know they would lower my compression. I'm looking for low end power, it's a street car. Am I better off sticking with the smaller heads? Thank you.
these heads have larger ports and valves than your gt40p's, and they're also significantly lighter. depending on your combination, you should see a significant power increase without a significant loss in low-end torque. the rockers are stud mounted, so they allow for adjustable valvetrain, and the springs are capable of withstanding a higher-lift cam than factory gt40p springs.